The major drawback of this app is that if any one can post something ( like-message, picture, video/audio clip) in your group and then he was decided the posted thing dont want to see anyone in that group then the sender delete that thing but the thing is delete in only their( sender) device and all group member( receiver) is see because all member are in group but this type of problem is not in facebook then I request to you please trace out this problem and then design proper query about that problem
The best use of this app is we can video call and use easily